Chapter 3 Precursors to Speech Copyright 2016 Wolters
Chapter 3 Precursors to Speech Copyright 2016 Wolters Kluwer All Rights Reserved 1 Chapter Goals 1. Identify the impacts of anatomic, motoric, sensory, cognitivelinguistic, and social precursors on speech development. 2. Describe typical developmental profiles associated with certain conditions and neurodevelopmental syndromes. 3. Describe influential models of speech production. Copyright 2016 Wolters Kluwer All Rights Reserved 2
Introduction to Physiologic, Cognitive, and Social Bases for Phonology Infant's auditory, articulatory, social, and cognitive capacities and experiences gradually increase. Some of these are necessary to build the foundation for successful, adult-like oral communication. We consider them in the following order: Motor Sensory Cognitive Social Copyright 2016 Wolters Kluwer All Rights Reserved 3 Anatomic and Motor Precursors
Four motor systems key to oral communication are: Respiration Resonance Phonation Articulation Prosody depends on intact functioning of all four. All immature anatomically, physiologically, or both at birth. Copyright 2016 Wolters Kluwer All Rights Reserved 4 Anatomic and Motor Precursors (cont.) Motor Programming and Planning Initially for a new task, the motor plan will be
constructed from scratch. A motor program is an abstract set of motor commands at the ready to be adapted to a particular task from the repeated use of a motor plan. Copyright 2016 Wolters Kluwer All Rights Reserved 5 Anatomic and Motor Precursors (cont.) Motor Planning Refers to generating appropriate set of signals sent
to muscles Result of dynamic, complex, context-specific process Includes coarticulation Initially (for new task), constructed from scratch Recalled for re-use (motor memory) Refined over time with practice Copyright 2016 Wolters Kluwer All Rights Reserved 6 Anatomic and Motor Precursors (cont.) Motor Programming Refers to more abstract general ability to make similar motor plans Reflects increases in speed, accuracy, and ability to adjust online while developing or carrying out new motor plan, resulting from motor memory of
many similar tasks Includes integration of multiple motor plans into larger wholes (e.g., combining words into sentences) Copyright 2016 Wolters Kluwer All Rights Reserved 7 Anatomic and Motor Precursors (cont.) Motor Programming and Planning (cont.) Terms motor program and motor plan seem to imply fixed entities (like music scores) but refer to very complex, dynamic, interactive processes. Imperfect terminology attempt to model fact that movement skill grows: From simpler patterns to more complex patterns
From rigid automatic movement patterns to flexible, dynamic responses to goals and contexts From isolated movements to more integrated movement patterns Copyright 2016 Wolters Kluwer All Rights Reserved 8 Anatomic and Motor Precursors (cont.) Motor Programming and Planning (cont) The motor and sensory systems work together to: Identify target configurations Relative sequence, timing, and placement Relative intensity, duration, and force Determine current state of articulators
Make motor programs/plans for production Store programs likely to be needed again Retrieve pre-existing programs Adjust pre-existing programs or plans in process to content and context Determine success of ongoing or completed plans and make adjustments to motor plan/program, as appropriate Copyright 2016 Wolters Kluwer All Rights Reserved 9 Anatomic and Motor Precursors (cont.) Functional Equivalence If certain motor plan not feasible, identify or create alternative appropriate to: Physical and physiological state
Linguistic context Other aspects of context Copyright 2016 Wolters Kluwer All Rights Reserved 10 Infant versus Adult Anatomy and Physiology Respiration Infant ribcage much smaller Mostly composed of cartilage Angled at 90 degrees to the spine Ribs rounded and raised
Diaphragm relatively flat; in adult, more juxtaposed to ribs Ribs eventually stiffen and lower and respiratory muscles increase in bulk Copyright 2016 Wolters Kluwer All Rights Reserved 11 Infant versus Adult Anatomy and Physiology (cont.) Articulation Tongue back in mouth near velum; contact with short, lower, wider, soft palate Forces infant to breathe nasally (obligate nose
breather) Poor independence of different parts of tongue Vocal tract at less steep angle Vocal tract configuration adult-like by age 6 Copyright 2016 Wolters Kluwer All Rights Reserved 12 Infant versus Adult Anatomy and Physiology (cont.) Copyright 2016 Wolters Kluwer All Rights Reserved 13 Reflexes Rooting: orientation of head
in direction of light touch stimulus in peri-oral area Typically followed or accompanied by mouthopening and sucking or swallowing movements Sucking: sucking movements stimulated by touch on palate Biting: mouth closing in response to light touch on anterior Copyright 2016 Wolters Kluwer All Rights Reserved 14 Muscle Tone Key to normal motor
function Abnormalities include: Low High Fluctuating Children may demonstrate low, high, or fluctuating muscle tone: Genetic syndromes Perinatal trauma (prenatal stroke, hypoxia) Prematurity Copyright 2016 Wolters Kluwer All Rights Reserved 15
Muscle Tone (cont.) Dysarthria Deficits in respiration, phonation, articulation, resonance, and/or prosody Result of damage or difference in neuromotor systems Often articulatory imprecision, due to abnormalities in motor neurons to tongue Speech rate often slower or irregular Copyright 2016 Wolters Kluwer All Rights Reserved 16 Key Communication-Related Motor Systems and Disorders Respiratory disorders
Cerebral palsy Broncho-pulmonary dysplasia Spina bifida Muscular dystrophy Anatomically-based resonatory and articulatory disorders Cleft palate High-arched palates Down syndrome Moebius syndrome Copyright 2016 Wolters Kluwer All Rights Reserved 17
Key Communication-Related Motor Systems and Disorders (cont.) Down syndrome Short hard palates Small oral cavities Tongues and lower jaws are normally sized Atypical facial musculature resulting in less flexibility with regard to facial expression and less fine motor control of the lips Oral-motor problems Hearing loss Linguistic-cognitive deficits
Sequential processing difficulties Motor speech deficits Altered parental input Copyright 2016 Wolters Kluwer All Rights Reserved 18 Key Communication-Related Motor Systems and Disorders (cont.) Copyright 2016 Wolters Kluwer All Rights Reserved 19 Key Communication-Related Motor Systems and Disorders (cont.)
Moebius syndrome Complete or partial paralysis of the facial nerve Palsy of the ocular, trigeminal, vagus, or glossopharyngeal nerves Hypoplasia of the tongue Oral-facial anomalies Limitations or inability to move the facial muscles for smiling, frowning, blinking, sucking, and speech Copyright 2016 Wolters Kluwer All Rights Reserved 20
Key Communication-Related Motor Systems and Disorders (cont.) Tongue tie (ankyloglossia) May cause speech production problems Insufficient research to advise best practices around clipping Copyright 2016 Wolters Kluwer All Rights Reserved 21 Sensory Functioning: Hearing Otitis
Media 16 times greater risk of speech-language delay Decreased comprehension of complex sentences Poorer phonemic and syllable awareness Immature speech perception Reduced verbal memory Effects seen as early as 14 to 16 months Impact also depends on: Socio-economic status Gender Language skills Hearing Loss, in general Decreased performance on:
Frequency discrimination Nonword repetition Word reading Copyright 2016 Wolters Kluwer All Rights Reserved 22 Sensory Functioning: Hearing (cont.) Cochlear implants Delayed phonetic repertoires (preschool to early school years) Decreased phonological awareness Literacy outcomes generally good
Copyright 2016 Wolters Kluwer All Rights Reserved 23 Sensory Functioning: Speech Perception At birth, infants already discriminate: Mothers voice
Prosody of own language (in conversation) Some vowels Different languages based on rhythm only # syllables per word (even if overall duration is same) Grammatical versus content words Probably due to amplitude, duration, and syllable structure differences At 1 to 2 months, infants discriminate: Pitch Duration Place, manner, and voicing of most consonants, even from other languages Syllables in disyllabic words ([badaba] vs. [bagaba]) At 4 months, infants discriminate: Own name Grammatical versus ungrammatical pauses in conversation At 6 months, infants discriminate: Words from own language (even if unfamiliar)
At 7 months, infants discriminate: Familiar words read in a passage, if trochaic (first syllable stressed) Copyright 2016 Wolters Kluwer All Rights Reserved 24 Sensory Functioning: Speech Perception (cont.) At 10 months, infants discriminate: Own language stress patterns Own language consonants Own language sequences of Cs and Vs More likely medial C sequences in own language Uninterrupted words At 10 to 12, months: Decreased ability to discriminate consonants not from
own language. Frequency of place of articulation in own language (alveolar vs. dorsal) has an impact on rate of decrease. Consistency of difference also has an effect. These abilities indicate that infants can detect distributional probabilities: Patterns of what occurs, where, and how often in own language. Copyright 2016 Wolters Kluwer All Rights Reserved 25 Sensory Functioning: Vision Speech perception also affected by vision: McGurk Effect Hear dadada when shown video of someone saying "gagaga" accompanied by synchronized
audio of "bababa." Even infants use vision to some extent when available for processing speech. Copyright 2016 Wolters Kluwer All Rights Reserved 26 Sensory Functioning: Tactile Sensitivity and Proprioception ASD, other disorders, long-term intubation, other negative oral experiences Hypersensitive and/or hyposensitive to touch either within and/or around oral area Difficulties with feeding, sensory-motor learning, and tolerance of speech therapy tactile cues
Copyright 2016 Wolters Kluwer All Rights Reserved 27 Sensory Functioning: SensoryMotor Connections Motor Sensory Receptors Muscle Spindles: alpha-gamma motor neuron system Alpha neurons to main muscle contract Gamma neurons to spindle contract Volume control Spasm if not in sync Provide sensory monitoring of motor performance Feedforward and feedback Sensory fibers found (so far) in: Tongue muscles Jaw closing muscles
Palatal muscles Subcortical and cortical association areas also integrate sensory and motor signals. Copyright 2016 Wolters Kluwer All Rights Reserved 28 Sensory Functioning: SensoryMotor Connections (cont.) Copyright 2016 Wolters Kluwer All Rights Reserved 29 Speech Production Models Gestural phonology
We do not produce speech sound by sound. We produce articulatory gestures. They overlapa lot! Coarticulation is predominant and normal. Copyright 2016 Wolters Kluwer All Rights Reserved 30 Speech Production Models (cont.) DIVA: Directions into Velocities of Articulators Feedforward Motor programs Abstract, general Somatosensory system senses current state of system Create motor plans
Context specific Precise Flexible Feedback Somatosensory system monitors output (alphagamma motor neuron system) Also auditory feedback Make corrections as appropriate Copyright 2016 Wolters Kluwer All Rights Reserved 31 Speech Production Models (cont.) Copyright 2016 Wolters Kluwer All Rights Reserved 32
Speech Production Models (cont.) Dynamic Systems Theory Complex interaction among factors Motor Perceptual/sensory Cognitive-linguistic External Instability normal part of process Imprecise plan Change in progress Therapy Stabilize whats emerging Then next thing can emerge Copyright 2016 Wolters Kluwer All Rights Reserved 33
Speech Production Models (cont.) What happens when motor and sensory systems dont communicate/ integrate? Example: Childhood Apraxia of Speech (CAS) Impacts planning/programming (feedforward) for speech production including ability to adjust motor plan on line based on feedback Precision and consistency of movements underlying speech impaired w/o neuromuscular deficits Probably neurologically based but subtly so Some genetic bases identified Also secondary diagnosis of certain other genetic neurobehavioral disorders: Autism Epilepsy Fragile X
Galactosemia Rett syndrome Copyright 2016 Wolters Kluwer All Rights Reserved 34 Speech Production Models (cont.) CAS (cont.) Three key speech features: Transitions between sounds or between syllables interrupted or lengthened Choppy quality Multiple repetitions of the same syllable, word, or phrase inconsistent productions Prosody, especially word stress, atypical Increased risk for expressive language and
phonological awareness difficulties Phonotactic problems especially common: Delayed or deviant syllable and word shapes Difficulties with multisyllabic words Worse performance with increasing length and complexity of utterance Copyright 2016 Wolters Kluwer All Rights Reserved 35 Cognitive (-Linguistic) Precursors to Speech Attention Critical for learning Attention deficits:
With hyperactivitydifficulty focusing for sustained periods Overfocused Memory Working memory capacity: How much can person hold in memory at once? Phonological memory: How well/long does person retain phonological details? Aspects of speakers accent, etc. Phonological content of nonsense words Non-word repetition Highly correlated with reading ability Learning Ability to make arbitrary associations Ability to generalize from specific concrete examples to abstract patterns Ability to recognize relationships between own and others actions Ability to imitate others actions
Copyright 2016 Wolters Kluwer All Rights Reserved 36 Cognitive (-Linguistic) Precursors to Speech (cont.) Mirror neurons Certain neurons fire in Broca area to control certain mouth or hand actions. A subset of these same neurons fire when the same actions are observed (carried out by other). Due to a sensory-motor connection? Based primarily on studies of macaques. Copyright 2016 Wolters Kluwer All Rights Reserved 37
Cognitive (-Linguistic) Precursors to Speech (cont.) Implicit Learning Expectations about frequencies of occurrence/probabilities of linguistic events Incidental = unintentional Occurs even without attention Infants as well as adults Both linguistic and non-linguistic stimuli Leads to development of abstract categories and representations Occurs after exposure to both natural and unnatural language systems Generalizations from specific instances to more abstract patterns occur in neocortical regions of brain Copyright 2016 Wolters Kluwer All Rights Reserved
38 Cognitive (-Linguistic) Precursors to Speech (cont.) Types of Learning Procedural (incidental) learning Slow and implicit Distributional probabilities : not consciously aware of tallying occurrences and contexts Not consciously aware of making generalizations Often relating to relationships: sequences, hierarchies, etc. Involves the neocortical portions of the brain (esp. the frontal lobe), in addition to the basal ganglia Children may have deficits in procedural learning/implicit learning
secondary to: ASD SLI Declarative memory Deliberate and/or conscious Remembering specific experiences as whole events Learn facts, word meanings Anything explicitly taught and/or learned Involves the hippocampus, thalamus, and portions of the temporal lobes Copyright 2016 Wolters Kluwer All Rights Reserved 39 Cognitive (-Linguistic) Precursors to Speech (cont.)
Copyright 2016 Wolters Kluwer All Rights Reserved 40 Cognitive (-Linguistic) Precursors to Speech (cont.) Copyright 2016 Wolters Kluwer All Rights Reserved 41 Social Precursors to Speech Communication depends on a triad
Meansability to communicate (all of above) Motive desire to communicate Communicative intent Rejecting/avoiding, requesting, giving, showing, greeting, and commenting Intents are less clear in children: With lower intelligence quotients In non-stimulating, unsupportive family environments With learning disabilities On the autism spectrum Opportunityreceptive communication partners Children are motivated to learn to communicate by: Desire to have needs met (request, reject) Social interaction: comment, participate, reciprocate When not acknowledged/understood, they may give up.
Copyright 2016 Wolters Kluwer All Rights Reserved 42 Social Precursors to Speech (cont.) Autism Spectrum Disorders Appear to lack motive: Decreased desire/ability to engage in social interaction Eye contact aversive Stimulus overselectivity Relate to others via irrelevant cues Inability/reduced ability to learn social cues May also lack means: Phonetic and phonological deficits very common Motor speech deficits
Poor prosody comprehension as well as production Poor procedural learning May also lack opportunity: Use atypical means not understood or not even acknowledged Copyright 2016 Wolters Kluwer All Rights Reserved 43 Summary Successful development of oral communication is impacted by intact anatomy; functional physiology; and neurologic control of sensorymotor integration, motor programming/planning, processing,
categorization, generalization, attention, and memory. Motive and opportunity are also required. Three models of speech production may be useful in conceptualizing development: gestural phonology, DIVA, and dynamic systems theory. Copyright 2016 Wolters Kluwer All Rights Reserved 44
Key Take-Home Messages 1. Speaking more than one language or dialect or a non-mainstream dialect is a linguistic difference, neither a delay nor a disorder. 2. Prerequisites are necessary antecedents of later development; precursors may contribute but are not crucial. 3. A wide variety of factors can affect speech development. 4. Purely motoric or purely cognitive-linguistic speech disorders are not the rule. 5. Theoretical speech production models can help us understand disorders. Copyright 2016 Wolters Kluwer All Rights Reserved 45
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